Callaghan, who has no previous criminal convictions, pleaded guilty to 14 counts of sexually abusing the sisters on various dates between January 1972 and January 1982 starting when the victims, two of whom were in court, were aged six, nine and 11 years of age respectfully.

A prosecution barrister told Judge Babington that the abuse took place in various houses in Derry at a time when the three victims were vulnerable.

The barrister said the abuse came to light in July 2014 when the three sisters reported the abuse to a social worker in Letterkenny Hospital. The following month the sisters made formal statements of complaint to the PSNI.

Callaghan was then interviewed by PSNI officers in March of last year when he denied the allegations.

The court was told that he told his doctor, "I did not think it was any harm".

Judge Babington told Callaghan: "This was appalling behaviour. This behaviour has to be met with an immediate sentence of imprisonment. You will be sentenced tomorrow."